1238 EARLE V. HARDENBURG 



the root system might develop at exactly the same depth. Therefore, in 

 studying this factor by reviewing experimental data, false conclusions 

 may easily be drawn. In studying it by survey methods, however, the 

 problem is not so complicated, because of the fact that approximately 

 the same system of culture is used thruout a given locality. 

 . Harwood (1893) reported a test of depth of planting conducted at the 

 Michigan station, using three varieties and planting on sandy loam soil. 

 The depth of planting was varied from 2 to 6 inches. The highest total 

 yield came from the 3-inch planting, while the 4-inch depth was second best. 

 The highest marketable yield came from planting 5 inches deep, altho there 

 was practically no difference between this and the 4- and 6-inch depths. 

 Emerson (1907) compared the yields from plantings at from 1- to 6-inch 

 depths, and obtained a constant increase in yield with each increase in 

 depth up to and including 5 inches. The 6-inch depth gave the second 

 highest yield. Emerson concluded that the better quality and shape of 

 the tuber resulting from planting from 4 to 5 inches deep, more than offset 

 the extra labor of digging necessary for these depths. Sandsten and 

 Delwiche (1909) harvested the highest total yield from the 4-inch depth of 

 p lanting, the yield decreasing with the increase in depth below that level. 

 Shepperd and Churchill (1911) compared the yields from plantings at 

 depths of 3, 4, 5, 6, 7, and 8 inches. The 4-inch depth gave 8 per cent 

 higher yield than any deeper planting, and 4.5 per cent more than the 

 3-inch depth. These investigators did not mention soil type, but reported 

 the greatest yield of marketable tubers and the highest quality from the 

 deeper plantings. 



Emerson (1914), studying the influence of depth of planting on the value 

 of the harvested crop for seed purposes, planted at 1, 4, and 7 inches. 

 Seed from the 7-inch planting yielded the best, both in total and in market- 

 able yield, in both of the tests he conducted. Also, seed from the 4-inch 

 planting yielded much better than did that from the 1-inch depth. Accord- 

 ing to Emerson, the higher quality of the seed from such deep planting is 

 probably due to the fact that it was produced under soil conditions which 

 fluctuated very little in temperature and moisture. 



Clement and Werner (1917) did not mention soil type in reporting a 

 six-years test on planting at depths of 3, 4, 5, 6, 8, and 10 inches. They 

 obtained the highest marketable yield from the 4-inch depth, and there was 

 a fairly consistent decrease in yield from plantings above and below that 

 depth. Macouri (1905) made a thoro test of the influence of depth of 

 planting, by comparing the yields for six years, on sandy loam soil, from 

 planting at depths of from 1 to 8 inches. In every one of the six years he 

 obtained the best yield from the 1-inch depth of planting. The second- 

 best average yield came from the 3-inch planting. Since Macoun explained 

 that cultivation during each season eventually placed the seed at a depth 

 of about 2J inches, it cannot be correctly concluded that 1 inch was a 



